In the welding industry, tremendous numbers of robotic welding stations are operable to draw welding wire from a package as a continuous supply of wire to perform successive welding operations. The advent of this mass use of electric welding wire has caused tremendous research and development in improving the packaging for the bulk welding wire. A common package is a drum where looped welding wire is deposited in the drum as a wire stack, or body, of wire having a top surface with an outer cylindrical surface against the drum and an inner cylindrical surface defining a central bore. The central bore is often occupied by a cardboard cylindrical core as shown in Cooper U.S. Pat. No. 5,819,934. It is common practice for the drum to have an upper retainer ring that is used in transportation to stabilize the body of welding wire as it settles. This ring, as is shown in Cooper U.S. Pat. No. 5,819,934, remains on the top of the welding wire to push downward by its weight so the wire can be pulled from the body of wire between the core and the ring. Each loop of wire has one turn of built-in twist, so that when it is payed out, the twist introduced by releasing a loop of wire is canceled. Hence, the wire is “twist-free” when it reaches the contact tip of the welding gun. The built-in twist causes the wire to spring up from the top of the stack when unrestrained. The weighted ring prevents wire from springing up due to the built-in twist. As a result, the weight of the ring is important. Heavier rings tend to bend or recast the wire, causing wire to wobble when it exits the contact tip, although they are more effective to prevent tangle. Lighter rings can be easily lifted by the wire during payout, thus losing its contact with the top of the wire stack and, thereby, losing its intended purpose of restraining wire movement at the top of the wire stack. Lighter rings have more propensity of tangle, although producing less wire wobble.
The preferred weight of the ring is dependent on the type of welding wire and the diameter or gauge of the welding wire. As can be appreciated, different materials have different properties and, therefore, can produce a different level of upward springing from the wire coil. In addition, changing the diameter of the welding wire will also change the properties of wire. As can also be appreciated, large diameter wire will have more “memory” than a smaller diameter wire. Memory is a measure of an object's tendency to seek a predetermined shape or configuration. As it pertains to this application, the tendency of the wire to seek its natural cast is greater with larger diameter wires. As a result, the ideal weight of the ring is dependent on a number of factors, including the type of welding wire and the diameter of the welding wire. This, in view of the fact that welding wire comes in many material compositions and diameters, creates a condition that a wide range of ring weights are needed to ideally control the payout or unwinding of the different wires, even if packaged in an identical welding wire package.
In addition to weight, the rigidity of the ring is also a factor. In this respect, if the ring flexes, based on the uneven upward forces produced by the wire coil, the ring can be less effective in the control of the unwinding of the welding wire. As can be appreciated, a flexing condition can be similar to the lifting condition described above, in that if the ring flexes or bends, at least a portion of the ring is misaligned from the ideal ring alignment on the top of the coil. While the ring may still be in contact with some of the coil top, a ring that flexes will not be in full contact and/or will allow the coil top to deform. The greater the amount of flex, the greater the misalignment or deformation. This can also result in an increased tendency of tangling and/or wobbling. Accordingly, some ring designs are preferably rigid designs. However, creating a rigid ring often requires either the use of complex and difficult-to-manufacture ring designs and/or the use of additional material which worsens the problem of controlling ring weight.
As can be appreciated from the above, one of the pitfalls of the weighted ring design is the difficulty of striking a balance of less tangle and less wire wobble. Tangles are detrimental to the operation of the package, since they cause downtime of the robotic welding station. Wobble is also detrimental to the operation of the package and can also adversely affect the weld itself by changing the condition of the wire flow through the welding torch. Tangles are caused by many adverse movements of the wire loops on top of the wire stack. The wire has a winding cast that can snap around the outside of the retainer ring, or the wire can bunch and slip at the inside of the retainer ring. The most common tangle is caused as wire is pulled from the inside of the ring and is referred to as “e-script” because of its shape. An e-script tangle stops operation of the welder and must be removed.